Patient comfort and practitioner efficiency remain paramount considerations within the healthcare industry. To this end, powered examination chairs featuring automatically moveable back, foot or other support surfaces have developed to facilitate clinical applications. Many such chairs may be positioned at a predetermined height above the floor. Support surfaces of the chair can often be manipulated to adjust the position of the person seated within, and many chairs can be lowered or raised in order to reduce the distance between a seated patient and the floor or healthcare professional.
An examination chair typically includes adjustable side rails positioned to restrain the movement of the patient seated in the chair. The side rails of the chair may e manually or automatically moved to a position away from the seat of the chair to facilitate the person getting in and out of the chair.
The speed at which a chair is designed to move is conventionally set at a nominal, or target speed. This target speed generally consists of a range of expected speeds, and is ideally optimized for efficient and predictable chair movement. As such, a voltage is supplied to a motor to produce a speed that generally falls within the target range. More particularly, the supplied voltage theoretically induces an amount of revolutions per minute in the motor that will cause the chair to generally move at the target speed.
However, the speed that conventional chairs actually move can vary dramatically from this target range. This inconsistency is often attributable to the weight of the patient or other some other load acting on the chair. The load incident on the chair causes the number of revolutions per minute to vary. The speed at which the chair moves reflects this variance. Namely, the load placed on the motor causes voltage to be diverted from its intended purpose of generating revolutions per minute.
Some conventional target speeds factor in the affect of an estimated load when determining the voltage or magnetic force level. Notably, this estimated load is a static figure. That is, the voltage is set according to a single, standard or median load. In this manner, voltage supplied to the motor of a conventional chair is set at a level that will generally achieve the target speed for a patient whom is precisely the standard weight.
The weight of patients, however, can vary dramatically from the standard weight estimate to which the motor is geared and powered. As the power level is set exclusively to the standard load, deviation from that standard load translates into the motor moving the chair at a rate that deviates from the target speed. That is, the chair moves at a faster or slower rate than the target speed. This variance and unpredictability poses an inconvenience and distraction to healthcare professionals and patients, alike.
Speed variance may also be encountered or exacerbated in circumstances where a chair is lowered or raised. Gravitational forces acting in concert with the patient and chair weight cause the motor to have to work relatively harder in order to raise the patient. Consequently, the speed of the chair is slower than the target speed when being raised. Conversely, the motor works less when lowering the chair. The speed of the chair is thus faster than the target speed when the chair is lowered.
As a consequence, what is needed is an improved manner of automatically adjusting the position of a power chair that mitigates the affect of load forces on chair/motor speed.